The lyrics are from rapper Mos Def's Mr Nigga, attacking society's distrust of black men who do well for themselves.

It carries the refrain: "Mr Nigga, Nigga, Nigga."

Ironically though, when it comes to using the controversial "N" word, Mos Def's line about the inequality between white and black can be turned on its head.

Many would say it's ok for a black person to speak it, but for a white person, it is definitely "suspect".

In the words of veteran rapper Ice T: "If you are it, you can use it." Yet many other black people would shudder at the mere whisper of it.

Surely, no other word in the English language can provoke such polarised reactions as "nigger", which is still widely seen as about the most vicious term of racist abuse there is.

Four years ago a (white) local government official in Washington DC was forced to resign for uttering "niggardly" in public. The word is not even related to "nigger" and the official was later reinstated.

In Britain, it could even be illegal - interpreted as an incitement to racial hatred.

Yet to some, especially in the US, it has actually become a term of affection between black men, the equivalent of "mate", "pal" or "buddy".

A new BBC radio documentary highlights how the word has been reinvented - some would say reclaimed - by the black community over the past 15 years.

The influence of black urban music has been at the centre of this recasting, with political rappers such as KRS-1 blazing the trail.

"KRS-1 always used it in the context of looking at it in a negative state of mind," says Chuck D, frontman with one of the most influential rap outfits ever, Public Enemy.

But it was groups like NWA - Niggaz With Attitude - who promoted a positive use of the word, in a effort to wrong-foot racists.

"They said if you are going to call me one, then I am one," says Chuck D.

Incredibly, the notorious "N" word gradually became accepted as a term of endearment between black friends.

Today, even black artists who are labelled more conscientious, such as soul singer Angie Stone, have adopted the term. "I don't have a problem with it," says Stone, "as long as it's used in an affectionate way."

Yet other black people remain astounded how an infamous racial slur can be bandied around so freely among those it was used to insult.

"People use it but have no idea about the historical baggage," says Professor Randall Kennedy (right), author of Nigger: The Strange Career of a Troublesome Word.

But confusion over use of the word doesn't stop there. Some argue its new found respectability is down to the difference in spelling - hip hop artists end the word with an "a" rather than "er".

And the fall-out over its use in Quentin Tarrantino's film Pulp Fiction - it got 15 mentions - highlighted how many consider the word ok when it is issued from black lips, but not those of a white person. Tarrantino wrote the script and speaks the word in a cameo role in the film.

Last year the same row was resurrected when Latino singer Jennifer Lopez spoke the "N" word in a track she recorded with black artist Ja Rule.

But the comments of rapper Pharoah Monch reveal how perhaps too much is being read into the word's new-found popularity.

For Monch, much of the word's appeal lies in its phonetic quality, and the fact it rhymes well.

"Sometimes I'll go over my words to find a better word, other times I'll just leave it there because phonetically, it fits."